<!DOCTYPE html>
<html>
<style>
body {
  height: 4000px;
  margin: 0;
  overflow: hidden;
}
#fixed {
  position: fixed;
  top: 50px;
  left: 50px;
  width: 100px;
  height: 100px;
  box-sizing: border-box;
  border: 1px solid blue;
}
</style>
<div id="fixed"></div>
</html>
